I'm not sure this is the case. Low-ISO cinema 35mm film (like Kodak VisionT 50D/250D) far exceeds SD resolution. How do you think Star Wars was ever scanned into 4k? Or 2001: A Space Odyssey? Film captures highlight detail logarithmically as well, while digital sensors still haven't really figured out how to render highlights well. This allows greater shadow detail with a skilled cinematographer with no loss of quality in brightly lit scenes. Theoretically, a single 35mm still can be scanned into 4k with no loss in detail, and higher-resolution scans won't lose quality -- there's just dimishing returns and in the end you might just be getting higher-res grain, but it is a far cry from standard definition.

Even 16mm can do HD scans just fine.

There's a reason Tarantino, Wes Anderson, PTA, Nolan, Sam Raimi, Scorsese, Spielberg, and David Lynch still swear by film (even though many of these directors have dabbled with digital). The idea that film is inherently "low-res" is a really frustrating and common misconception among younger generations unfamiliar with the technology. I find it kind of unbelievable that DPs would shoot 35mm just for an SD scan. That type of use case seems better suited for mini-DV or other contemporary video formats.

This probably was also to deal with period TV cameras. Video cameras of that time couldn’t deal with bright lights and had terrible dynamic range. CCDs improved this a lot. Direct to video productions looked cheap.

They shot 35mm for the big screen.